The present invention relates to inter-network switching for packet switching network, and in particular to an inter-network routing control method capable of selecting the optimum gate station and the optimum inter-network circuit.
As prior art relating to inter-network routing control, a technique described in JP-A-63-224441, for example, is known.
When the optimum gate device is to be selected at the time of inter-network switching in the prior art, respective calling terminals store states of gate devices and a calling terminal directly selects a gate device, specifies the address of that gate device as the called address for inter-network relay, and issues a call.
In case the above described prior art is applied to a packet switching network, that packet switching network is so configured that a switch station accepting a call from a terminal may store and update states of all gate stations included in the packet switching network, select a gate station by referring to the states at the time of inter-network switching, and transfer a call request. Further, the packet switching network is so configured that the following operation may be performed. When the selected gate station cannot be connected to another network, that gate station returns busy information to the calling station and the calling station which has received the busy information selects another gate station and retransfers the call request.
In a packet switching network using such a method, a burden upon the switch station is heavy, and in addition all of gate station information defined on respective switch stations must be replaced when the configuration of the gate stations is to be changed, resulting in a problem of lack of flexibility as the system.